\[3x^{2} - 5x - 8 = 0\]
\[D = ( - 5)^{2} - 4 \cdot 3 \cdot ( - 8) =\]
\[= 25 + 96 = 121\]
\[x_{1} = \frac{5 + \sqrt{121}}{2 \cdot 3} = \frac{5 + 11}{6} = \frac{16}{6} =\]
\[= \frac{8}{3} = 2\frac{2}{3}\]
\[x_{2} = \frac{5 - \sqrt{121}}{2 \cdot 3} = \frac{5 - 11}{6} =\]
\[= \frac{- 6}{6} = - 1\]
\[Ответ:2\frac{2}{3};\ - 1.\]